1. Field of the Invention
The present invention relates to a manufacturing method for a monolithic ceramic electronic component, and more specifically, to a method for forming a protective area at the side of internal electrodes in a monolithic ceramic electronic component.
2. Description of the Related Art
A monolithic ceramic capacitor exists as an example of a monolithic ceramic electronic component to which the present invention is directed. To manufacture a monolithic ceramic capacitor, typically, a step as illustrated in FIGS. 22A and 22B is performed. That is, a first ceramic green sheet 3 on which a first internal electrode 1 is formed, and a second ceramic green sheet 4 on which a second internal electrode 2 is formed are alternately stacked in a plurality of layers. A raw component body is obtained by this stacking step. After the raw component body is fired, first and second external electrodes are formed on opposing first and second end surfaces of the sintered component body. Thus, the first and second internal electrodes 1 and 2 led out to the first and second end surfaces are electrically connected to the first and second external electrodes, respectively, and a monolithic ceramic capacitor is completed.
In recent years, monolithic ceramic capacitors are steadily decreasing in size, while monolithic ceramic capacitors that can provide high capacitance are being desired. To meet such a demand, it is effective to increase the effective area occupied by each of the internal electrodes 1 and 2 on the stacked ceramic green sheets 3 and 4, that is, the opposing area of the internal electrodes 1 and 2. To increase such an effective area, it is important to reduce the dimensions of a protective area 5 at the side and the dimensions of a protective area 6 at the end illustrated in FIGS. 22A and 22B.
However, reducing the dimensions of the protective area 6 at the end undesirably increases the risk of short-circuiting of the first external electrode and the second external electrode via either one of the internal electrodes 1 and 2. Accordingly, it is appreciated that considering the reliability of the monolithic ceramic capacitor, it is more preferable to reduce the dimensions of the protective area 5 at the side than to reduce the dimensions of the protective area 6 at the end.
An example of an effective method for reducing the dimensions of the protective area 5 at the side is described in Japanese Unexamined Patent Application Publication No. 3-108306. According to the method described in Japanese Unexamined Patent Application Publication No. 3-108306, a laminate is prepared which has a laminated structure including a plurality of ceramic layers and a plurality of internal electrodes that are in a raw state, with the internal electrodes being exposed on its side surface, and this laminate is dipped in a ceramic slurry to thereby form the protective area at the side.
However, the technique described in Japanese Unexamined Patent Application Publication No. 3-108306 mentioned above has the following problems.
That is, when dipping the laminate in the ceramic slurry, the ceramic slurry is also applied onto a surface of the laminate other than the surface that is to become the protective area at the side, for example, the principal surface. Moreover, in the case of applying the ceramic slurry by dipping, the control for making the thickness of the applied ceramic slurry uniform is not easy. For example, as illustrated in FIG. 23, when a ceramic slurry 8 is applied to a laminate 7, owing to the surface tension acting on the ceramic slurry 8, at corners 9 of the laminate 7, the applied thickness of the ceramic slurry 8 tends to become thin, making it difficult to secure a desired applied thickness. For these reasons, water tends to enter from the corners 9, leading to a decrease in reliability in some cases. Moreover, the monolithic ceramic capacitor obtained is prone to dimensional variations.
Similar problems can be encountered not only when manufacturing monolithic ceramic capacitors but also when manufacturing monolithic ceramic electronic components other than monolithic ceramic capacitors.